Leptospirosis is an infectious disease caused by a type of bacteria called Leptospira. The disease causes serious damage to the kidney and liver, and may be fatal in severe cases. Bacteria are passed in the urine of infected animals and can survive in the environment for long periods of time in warm, stagnant water or moist soil. Wild animals, including skunks, raccoons, opossums, rats, wolves, and deer, can spread infection to dogs.